Doctors could save three million more lives worldwide by 2025 if they offer AIDS drugs to people with HIV much sooner after they test positive for the virus, the World Health Organisation (WHO) says.

While better access to cheap generic AIDS drugs means many more people are now getting treatment, health workers, particularly in poor countries with limited health budgets, currently tend to wait until the infection has progressed.

But in new guidelines aimed at controlling and eventually reducing the global AIDS epidemic, the United Nations health agency said some 26 million HIV-positive people - or around 80 per cent of all those with the virus - should be getting drug treatment.

The guidelines, which set a global standard for when people with human immunodeficiency virus (HIV) should start antiretroviral treatment, were drawn up after numerous studies found that treating HIV patients earlier can keep them healthy for many years and also lowers the amount of virus in the blood, significantly cutting their risk of infecting someone else.

Key points

An estimated 34 million people worldwide are HIV positive

New guidelines mean 26 million people should get treatment

AIDS drugs can keep people healthy and stop HIV spreading

25 million people with AIDS have died in the 30 years since HIV was first discovered

Medecins Sans Frontieres says money and political will are required to deliver the changes

"We are raising the bar to 26 million people," WHO HIV/AIDS department director Gottfried Hirnschall said.

"And this is not only about keeping people healthy and alive but also about blocking further transmission of HIV."

Some 34 million people worldwide have the HIV virus that causes AIDS and the vast majority of them live in poor and developing countries. Sub-Saharan Africa is by far the worst affected region.

But the epidemic - which has killed 25 million people in the 30 years since HIV was first discovered - is showing some signs of being turned around.

The United Nation's AIDS program UNAIDS says deaths from the disease fell to 1.7 million in 2011, down from a peak of 2.3 million in 2005 and from 1.8 million in 2010.

Swift progress has also been made in getting more HIV patients into treatment, with 9.7 million people getting life-saving AIDS drugs in 2012, up from just 300,000 people a decade earlier, according to latest WHO data.

Indian generics companies are leading suppliers of HIV drugs to Africa and to many other poor countries.

International support to fund the change 'critical'

Margaret Chan, the WHO's director general, said the dramatic improvement in access to HIV treatment raised the prospect of the world one day being able to beat the disease.

"With nearly 10 million people now on antiretroviral therapy, we see that such prospects - unthinkable just a few years ago - can now fuel the momentum needed to push the HIV epidemic into irreversible decline," she said.

The WHO's guidelines encourage health authorities worldwide to start treatment in adults with HIV as soon as a key test known as a CD4 cell count falls to a measure of 500 cells per cubic millimetre or less.

The previous WHO standard was to offer treatment at a CD4 count of 350 or less, in other words when the virus has already started to damage the patient's immune system.

The guidelines also say all pregnant or breastfeeding women and all children under five with HIV should start treatment immediately, whatever their CD4 count, and that all HIV patients should be regularly monitored to assess their "viral load".

This allows health workers to check whether the medicines are reducing the amount of virus in the blood. It also encourages patients to keep taking their medicine because they can see it having positive results.

"There's no greater motivating factor for people to stick to their HIV treatment than knowing the virus is undetectable in their blood," Medecins Sans Frontieres (MSF) South African coordinator Gilles van Cutsem said.

MSF welcomed the new guidelines but cautioned that the money and the political will to implement them was also needed.

"Now is not the time to be daunted but to push forward," MSF president Unni Karunakara said in a statement.

"So it's critical to mobilise international support... including funding for HIV treatment programmes from donor governments."

Mr Hirnschall said getting AIDS drugs to the extra patients brought in by the new guidelines would require another 10 per cent on top of the $24 billion a year currently needed to fund the global fight against HIV and AIDS.

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